One
can manually increase or decrease size of a datafile from Oracle 7.2 using
command.
SQL>ALTER DATABASE DATAFILE 'filename2' RESIZE 100M;
Because one can change the sizes of data files, one can add more space to your database without adding more datafiles. This is beneficial if concerned about reaching the maximum number of datafiles allowed in your database
Manually reducing the sizes of datafiles allows one to reclaim unused space in the database. This is useful for correcting errors in estimations of space requirements.
Also, datafiles can be allowed to automatically extend if more space is required.
Command
SQL>CREATE TABLESPACE pcs_data_ts
DATAFILE 'c: \ora_apps\pcs\pcsdata1.dbf' SIZE 3M
AUTOEXTEND ON NEXT 1M MAXSIZE UNLIMITED
DEFAULT STORAGE (INITIAL 10240
NEXT 10240
MINEXTENTS 1
MAXEXTENTS UNLIMITED
PCTINCREASE 0)
ONLINE
PERMANENT;